How to use gprof to generate gmon.out while running the program

How to use gprof to generate gmon.out while running the program

• The function "monstartup" is used to reinitialize the data block used by gmon to collect profile data.
• The function "_mcleanup"  writes profile data to gmon.out
• Change the current direct to /tmp to place the gmon.out to the default folder /tmop
• After finish the test revert the current folder.
• Send the SIGUSR2  signal to the process to generate the gmon.out file.
• Generate the gmon.out file
• send the signal using below
• $kill -s SIGUSR2 26908
• See the output in below folder
• $cd /tmp

Example Program:

Program file 1: gprof_test-signal.c

#include<stdio.h>

#include<stdlib.h>

#include <dirent.h>

#include <sys/gmon.h>

#include <signal.h>

#include <string.h>

void write_gmon_out_file();

void sigusr2_handler(int sig);

void gprof_init(void);

/* Beginning and end of our code segment.  */

extern void _start (void), etext (void);

/*

 * This function uses APIs from the gmon library which is part of the

 * the standard glibC library, to force write the profile data.

 * The function "monstartup" is used to reinitialize the data block

 * used by gmon to collect profile data.

 * The function "_mcleanup"  writes profile data to gmon.out

 */

void write_gmon_out_file (void)

{

    char *gmon_dir = "/tmp";

    char originalDir[256];

    if (getcwd(originalDir, 256) == '\0') {

        printf("Failed to get original working directory... \n");

        memset(originalDir, 0, 256);

    }

    else {

        printf("Original Dir = %s \n", originalDir);

    }

    if (chdir(gmon_dir) == 0) {

        printf("Successfully changed to dir = %s \n", gmon_dir);

    }

    else {

        printf("Failed to change to dir = %s \n", gmon_dir);

    }

    _mcleanup();

    monstartup((unsigned long ) &_start, (unsigned long ) &etext);

    if (originalDir[0] != 0) {

        printf("Switching to original working dir ...\n");

        chdir(originalDir);

    }

    return ;

}

void sigusr2_handler(int sig)

{

    printf("Received Signal: %d\n", sig);

    write_gmon_out_file() ;

    signal(SIGUSR2, sigusr2_handler) ;

}

void gprof_init(void)

{

    signal(SIGUSR2, sigusr2_handler) ;

    printf("GPROF SIGNAL HANDLER INITIALIZED\r\n");

    sleep(5);

}

void new_func1(void);

void func1(void)

{

    printf("\n Inside func1 \n");

    int i = 0;

    //exit(0);

    sleep(10);

    for(;i<0xffffffff;i++);

    new_func1();

    return;

}

static void func2(void)

{

    printf("\n Inside func2 \n");

    int i = 0;

    for(;i<0xffffffaa;i++);

    return;

}

int main(void)

{

    printf("\n Inside main()\n");

    int i = 0;

     gprof_init();

    for(;i<0xffffff;i++);

    func1();

    func2();

    return 0;

}

Program 2: gprof_test_2.c

//test_gprof_new.c

#include<stdio.h>

void new_func1(void)

{

    printf("\n Inside new_func1()\n");

    int i = 0;

    for(;i<0xffffffee;i++);

    return;

}

Output:

Execute the program:

gprof$ ./a.out

 Inside main()

GPROF SIGNAL HANDLER INITIALIZED

 Inside func1

Received Signal: 12

Original Dir = /home/labuser/velrajk/sample/gprof

Successfully changed to dir = /tmp

Switching to original working dir ...

---- output file.

$cd /tmp

$ ls gmon.out 

gmon.out

$